Adjustable syringe assemblies

ABSTRACT

An adjustable syringe assembly capable of adjusting the extent to which fluid is drawn into a syringe. A plunger of the syringe is engaged by a pusher which is guided by a support releasably connected with a barrel of the syringe. This support carries a stop which is adjustably fixed to the support in the path of movement of part of the pusher so as to adjust the extent to which the plunger is displaced along its suction stroke.

Unlted States Patent 1191 1111 3,831,602 Broadwin Aug. 27, 1974 [54] ADJUSTABLE SYRINGE ASSEMBLIES 2,959,170 11/1960 Laub 128/218 N 1 Inventor Samuel Bmadwin, New York, 311231512 @1132? fifi tfa' iitijiijj '31:: 133/5635 73 i Union p i Corporation, 3,261,509 7/1966 Shevell 222/309 Springfield, NJ. 3,327,904 6/1967 Goda et a1. 128/218 c Filed: 11, 1972 Primary Examiner-Richard A. Gaudet [21 AppL 225 505 Assistant Examiner-1. C. McGowan Attorney, Agent, or Fzrm--Stemberg & Blake [52] US. Cl. 128/218 F, 128/218 C, 128/218 PA, [57] ABSTRACT 222 309 51 1m. (:1 A61m 5 22 An adjustable y ng ssembly capable of adjusting [58] Field of Search 128/218 F, 218 c, 218 PA, the extent to hi fluid is drawn into a syringe. A 128015 218 222/309 340 plunger of the syrmge 1s engaged by a pusher WhlCh 1s guided by a support releasably connected with a barrel 56] References Cited ofSgagyt1jngtTl31s sglpportrtcarrtilels a; stfipozyhich is ad;

]U me o e uppo 1n e a movemen UNITED STATES PATENTS of part of the pusher so as to adjust the extent to 1,569,457 l/ 1926 Carstens 128/218 C which the plunger is displaced along its Suction Stroke 2,047,010 7/1936 D1ckmson.... 128/215 2,705,494 4/1955 Broadwin 128/218 F 2 Claims, 8 Drawing Figures PATENIED nus 2 11974 sumwrz PATEmfnauczmm sum as: 3

l 45 IHH v H62 1 ADJUSTABLE SYRINGE ASSEMBLIES BACKGROUND OF THE INVENTION The present invention relates to syringes.

In particular, the present invention relates to syringes which can be adjusted for determining the extent to which fluid is sucked into and discharged therefrom.

As is well known, a conventional syringe includes a barrel and a plunger for drawing fluid into the barrel during a suction stroke of the plunger and for discharging fluid from the barrel during a pressure stroke of the plunger. The plunger must be very carefully moved with respect to the barrel in order to make certain that the desired amount of fluid is accurately drawn into the barrel. This extreme care which must be exercised in connection with the operation of a conventional syringe presents a great inconvenience. This latter inconvenience becomes a very substantial drawback in the case where a syringe must be used repeatedly in order to draw precisely the same amount of fluid into the syringe at each stroke of the plunger.

There are various situations encountered where a syringe is used repeatedly under these conditions. For example, there are situations where the same dose of a given fluid is to be repeatedly injected into a number of patients, for example, so that a physician, nurse or the like must repeatedly exercise the above extreme care to make certain that precisely the right amount of fluid is drawn into the syringe at each use thereof. In addition there are situations where mechanical structures cooperate with a syringe to operate the latter mechanically so as to provide cycles during each of which a given amount of fluid is to be drawn into the syringe from one container and expelled from the syringe into another container. In this latter situation, it may be necessary, for example, to add precisely determined amounts of liquid to a number of individual containers, and manual operation of a syringe under these conditions represents a great loss of time and increased labor costs.

Moreover, the above situation is aggravated by the fact that during one series of operations one amount of fluid may be required to be repeatedly drawn into and expelled from a syringe while during a following series of operations a different amount of fluid is tobe drawn in and expelled from a syringe. Under these latter conditions, the changeover from the first amount which is repeatedly drawn in and expelled to the second amount which is repeatedly drawn in and expelled represents a further extreme inconvenience which is encountered at the present time with conventional syringes.

SUMMARY OF THE INVENTION It is accordingly a primary object of the present invention to provide a syringe assembly which will avoid the above drawbacks.

In particular, it is an object of the present invention to provide a syringe assembly which makes it possible to set the assembly in such a way that once it is set it can be operated rapidly and conveniently to repeatedly draw in a precisely determined amount of fluid which is repeatedly expelled, so that the above inconvenience is eliminated.

Furthermore, it is an object of the present invention to provide an assembly of this type which can be readily 2 adjusted so as to change the precisely determined amount of fluid which is drawn into the syringe.

Yet another object of the present invention is to provide a structure of the above type which can be used with a conventional syringe.

In particular, it is an object of the invention to provide a relatively simple inexpensive structure which can be attached to a conventional syringe so as to eliminate all of the drawbacks referred to above.

Yet another object of the present invention is to provide an inexpensive structure of this type which can be attached to different types of conventional syringes for eliminating the above drawbacks even though different types of syringes are used.

According to the invention the syringe assembly includes a barrel having one end through which fluid is drawn into and expelled from the barrel, this barrel having an opposed open end though which a plunger means extends into the barrel for movement toward the one end thereof during the pressure stroke while fluid is discharged and in an opposite direction along a suction stroke in order to draw fluid into the barrel. A spring means coacts with the plunger means to urge the latter along its suction stroke. An elongated support means is fixed by a releasable connecting means to the barrel at the region of the opposed open end thereof referred to above, and this elongated support means supports a pusher means for movement along the axis of the barrel while engaging the plunger means so as to push the latter along its pressure stroke in opposition to the spring means, the pusher means being released to permit the spring means to expand in order to retract the plunger means along its suction stroke while returning the pusher means toward a predetermined starting position thereof. An adjustable stop means is carried by the support means to be located thereon at a selected location in the path of movement of the pusher means so as to determine the extent to which the plunger means is retracted along its suction stroke by the spring means. Thus, by locating the stop means at a selected location along the support means it is possible to determine in a highly precise manner the suction stroke of the plunger means when it is released from the pushing force of the pusher means, and in this way precisely determined amounts of fluid can be repeatedly drawn into the barrel to be susequently expelled therefrom by the action of the pusher means.

BRIEF DESCRIPTION OF DRAWINGS The invention is illustrated by way of example in the accompanying drawings which form part of this appli cation and in which:

FIG. I is a front elevation of one possible syringe assembly according to the present invention;

FIG. 2 is a longitudinal sectional elevation of the structure of FIG. 1 taken along line 2-2 of FIG. I in the direction of the arrows;

FIG. 3 is a transverse sectional plan view taken along line 3-3 of FIG. 1 in the direction of the arrows;

FIG. 4 is a fragmentary partly sectional elevation showing a variation of the structure of FIG. 2;

FIG. 5 is a transverse sectional plan view taken along line 5-5 of FIG. I in the direction of the arrows;

FIG. 6 is a transverse sectional plan view showing a variation of the structure of FIG. 5;

FIG. 7 is a partly sectional fragmentary elevation showing a variation of the releasable connecting means of FIGS. 1 and 2, and

FIG. 8 is a fragmentary elevation of a further embodiment.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to FIG. I, the syringe assembly 10 of the present invention which is illustrated therein includes an elongated barrel 12 which may be made of a transparent plastic carrying suitable graduations 14, as

is well known. This barrel 12 has a lower end 16 through which fluid is drawn into and discharged from the barrel 12. If desired this end I6 may be provided with the valve assembly 18. This assembly 18 has oneway valves 20 and 22 so that, for example, through a flexible tubular member 24 fluid can be drawn into the barrel 12 during a suction stroke of a plunger which moves therein but cannot discharge through the valve 20, while during a pressure stroke of the plunger fluid will discharge through the valve 22 which does not per-.

mit fluid to be drawn in through the valve 22. In this way through the tube 24 a fluid may be drawn out of one container into the barrel l2 and then during the pressure stroke of the plunger the fluid can be discharged through the valve 22 into another container.

The elongated barrel l2 has at its top end a flange 26 which has in the illustrated example opposed curved side edges 28 (FIG. 3) and a pair of opposed extensions 30 which project laterally from the barrel at the top open end thereof, as viewed in FIGS. 1 and 2.

An elongated plunger means 32 extends into the barrel 12 through the top open end thereof. This plunger means terminates at its bottom end in a piston member 34 which has a slidable fluid-tight engagement with the inner surface of the barrel as is well known. From the piston member 34 the plunger means has an elongated shank extending upwardly beyond the barrel l2 and formed in the illustrated example by intersecting walls 36 which are perpendicular to each other and which extend along the axis of the barrel 12. These walls 36 which are perpendicular to each other are connected at their top end to a flange 38 shown most clearly in FIG. 2. This flange 38 extends beyond the outer edges of the fins or mutually perpendicular intersecting walls 36 which form the part of the plunger means 32 to which the piston 34 is fixed.

A spring means 40 coaets with the plunger means 32 for urging the latter along its suction stroke which takes place when the piston 34 moves upwardly away from the lower end 16 of the barrel 12. This spring means 40 is in the form ofa coil spring which is coiled about the intersecting walls 36 of the plunger means 32. The coil spring has a top end engaging the flange 38 and a bottom end engaging an upwardly directed surface at the top end of the barrel 12. This surface is surrounded by the flange which forms the extensions 30 shown in FIG. 3. Thus, the spring 40 constantly seeks to urge the plunger means 32 upwardly along its suction stroke.

In accordance with the present invention an elongated support means 42 is releasably connected with the barrel 12 at the region of its top open end. This support means 42 is in the form of an elongated tubular member which has a bottom end located at the region of the top open end of the barrel 12. The tubular support means 42 may have at its bottom end, in the example illustrated in FIGS. 1-3, a pair of opposed notches 44 through which the extensions 30 at the top end of the barrel can pass. The walls of the tubular support means 42 between these notches, which extend axially from the bottom end of the tubular support means 42, are formed with short circumferential notches 46 which communicate with the noches 44 at the top ends of the latter. Thus, once the extensions 30 are placed in the notches 44, the barrel can be turned to locate portions of the extensions 30 in the notches 46, and thus a bayonet connection is made by this releasable connecting means between the bottom end of the tubular support means 42 and the top end of the barrel 12.

The tubular support means 42 serves to support for movement along the axis of the barrel 12 an elongated pusher means 48. This pusher means 48 has a structure resembling that part of the plunger means 32 which extends upwardly beyond the piston 34. Thus, the pusher means 48 itself is composed of a pair of intersecting walls 50 and 52 which are perpendicular to each other. The tubular support means 42 terminates at its top end in a top wall 54 which is formed with a pair of intersecting slots through which the intersecting walls 50 and 52 slidably extend. The pair of intersecting walls 50 and 52 are fixed at their top ends to a transverse flange 56 which provides a flat outer end surface for the pusher means. This surface 58 can be manually engaged or it may be actuated by a rotary cam, for example.

In the hollow interior of the tubular support means 42 the walls 50 and 52 of the pusher means 48 are fixed to a flange 60 which extends across the interior of the tubular support means 42 and which directly engages the top flange 38 at the top end of the plunger means 32.

The elongated tubular support means 42 is formed with a longitudinally extending slot 62 which extends substantially through the length thereof, as is particularly apparent from FIGS. 1 and 2. The flange 60 at the bottom end of the pusher means has an extension 64 which extends through and beyond the slot 62. In this slot 62, above the projection 64 of the pusher means there is a stop means 66 which is adjustable along the slot 62 and which is situated at a selected location therealong by a releasable fixing means. The stop means 66 includes a substantially T-shaped member 68 (FIG. 5) which has one leg in the interior of the tubular support means 42 extending across the slot 62 and which has a second leg extending through the beyond the slot 62. This second leg of the T-shaped member 68 is itself formed with a horizontal notch 70. In this notch 70 is.located a strap 72 which extends across the slot 62 at the exterior of the tubular support means 42. The tubular support means 42 may be providedalong the edges of the slot 62 at the exterior of the tubular support means with a pair of longitudinally extending lips 74, and the strap 72 may terminate at its opposed ends in a pair of extensions 76 between which these lips are located, as in most clearly apparent from FIG. 5.

The releasable fixing means for the adjustable stop means includes an elongated screw member 78 fixed to the T-shaped member 68, extending therefrom centrally through the notch 70 in the leg which extends through and beyond the slot 62, and this screw 78 extends through a central opening of the strap 72. Beyond the strap 72 the screw 78 carries a nut 80 provided, for example, with the knurled head so that the operator can conveniently turn this nut. Thus, by loosening the nut 80 it is possible to loosen the strap 72 and member 68 so that they can be shifted along the edges of the slot 62 to a desired location therealong, and once this location is reached the nut 80 can be tightened so as to releasably fix the stop means 66 at a selected location along the slot 62.

The above described structure operates as follows:

With the parts assembled as shown in FIGS. 1 and 2, the operator can depress the pusher means 48 so as to move the piston 34 downwardly along its pressure stroke in opposition to the spring 40 which becomes compressed, the bottom end 60 of the pusher means 48 engaging the top end 38 of the plunger means so as to transfer downward movement of the pusher means to the plunger means. In order to render this movement convenient the support means 42 may have a pair of extensions 82 at its top end suitably curved to be engaged by the first and second fingers of the hand of the operator while the thumb of the operator can engage the top surface 58 of the pusher means 48. Thus, the entire pusher means will be displaced downwardly along the interior of the tubular support means 42, displacing the plunger means 32 downwardly in opposition to the spring 40, and this movement is continued until the plunger means reaches the bottom end of its pressure stroke when the piston 34 is located at its position closest to the discharge end 16 of the barrel 12. Then the operator will simply release the pusher means 42. The result is that thespring 40 will expand, returning the parts toward their starting position such as that illustrated in FIG. 2. The spring 40 will continue to expand, by displacing the plunger means 32 along its suction stroke so as to draw fluid into the barrel 12. This movement will continue until the projection 64 engages the stop means 66. Thus, by properly positioning the stop means 66 a precisely determined amount of fluid will be drawn into the barrel 12. Then during the next pressure stroke this fluid will be expelled and upon release of the plunger means the spring 40 will again expand so as to repeat this operation. Therefore, by properly positioning the stop means 66 it is possible to repeatedly draw into the barrel 12 a precisely determined amount of fluid which is subsequently expelled therefrom, and these operations can be repeated as often as desired with a high degree of accuracy and a minimum of inconvenience. As was pointed out above, instead of operating the structure manually it is possible to adapt it for use with a mechanically operating structure where a cam, for example, will engage the surface 58 to displace the pusher means 48 in the direction which pushes the plunger means 32 along its pressure stroke, this cam then releasing the pusher means so that the spring 40 can expand to bring about the above operations in a mechanical manner.

As is indicated in FIG. 4, the above-described structure may be varied by mounting a rotary screw member 84 on the projection 64. This screw member can simply be threaded through the projection 64 so that the top free end of the screw 84 can engage the lower surface of the stop means 66. Thus, once the stop means 66 has been placed in what is believed to be an accurate posi tion, it is possible by turning the screw 84 to provide an extremely fine control of the extent to which fluid will be drawn into the barrel 12 during each suction stroke.

All of the above components may be conveniently made of plastic. As is illustrated in FIG. 5, the tubular support means 42 may be made of a pair of plastic components 42a and 4212 having aligned ears 86 which engage each other and which are connected by rivets 88, so that in this way the parts can be maintained in assembled condition.

However, instead of such an arrangement it is possible to use an arrangement as shown in FIG. 6 where the two components 420 and 42d of the tubular support means 42 have interlocking projections for assembling the components of the tubular support means. Thus, the part 420 may have at its opposed side edges elongated tongues 90 which can snap into springy grooves 92 carried by the component 42d.

Furthermore, the exterior surface of the tubular support means 42 at the region of its lower end may be provided with exterior threads 94, as shown in FIGS. 1 and 7. These exterior threads 94 are adapted to coact with the interior threads of a cap nut 96. This cap nut 96 has a bottom circular flange 98 through which the barrel 12 extends. With this construction the barrel 12 can terminate at its top end in a simple circular flange 100 which engages the bottom end surface of the tubular support means 42 with the flange of the cap nut 96 engaging the flange 100 to press the latter against the bottom end of the tubular support means 42, so that with this arrangement by the addition of the simple cap nut 96 it is possible to utilize instead of the bayonet connection to FIGS. ll-3 a threaded cap nut connection as shown in FIG. 7. In this way the structure is adapted to be used with syringes of different types. It is to be noted that the flange 100 can have a considerable variation in its outer diameter while still being capable of engaging the flange 98 and pressed against the bottom end of the tubular support means 42, so that through a considerable range of flange diameters it is still possible to use one embodiment of the assembly structure of the invention which is used in addition to the conventional syringe structure.

As may be seen from FIG. 8, the ribs 62' of this embodiment, which otherwise is identical with that of FIG. 2, for example, are formed with notches 100, and the notches of one of the ribs 62 are in horizontal alignment with the notches of the other rib. The strap 72 is replaced by a strap 102 provided with relatively sharp edges 104 to be received in a pair of successive notches 100 of each rib 62'. In this way the stop means will be reliably held in a selected position. In the event that it is desired to provide adjustments between these positions, then an adjusting screw 84 as shown in FIG. 4 may be used.

What is claimed is:

l. A syringe assembly comprising an elongated barrel having one end through which fluid enters into and discharges from said barrel and an opposed open end distant from said one end, plunger means extending through said opposed open end of said barrel into the interior thereof for movement along a pressure stroke in the interior of said barrel toward said one end thereof for discharging fluid from said barrel and for movement in an opposite direction away from said one end thereof along a suction stroke for sucking fluid into said barrel, spring means engaging said barrel and plunger means for urging the latter along said suction stroke thereof, elongated support means extending longitudinally along said plunger means beyond said opposed open end of said barrel and having an end region situated adjacent the latter end of said barrel, connecting means coacting with said elongated support means and said barrel for releasably fixing said elongated support means to said barrel at the region of said opposed open end thereof, pusher means carried by said elongated support means for engaging and pushing said plunger means in opposition to said spring means along said pressure stroke for discharging fluid out of said barrel through said one end thereof, said pusher means when released from pushing said plunger means along said pressure stroke thereof being returned by said spring means toward a starting position simultaneously with retraction of said plunger means along said suction stroke thereof by said spring means, and adjustable stop means fixedly connectable to said elongated support means at a selected location along the path of movement of said pusher means when released, and mot moving with said pusher means, for limiting the extent to which said pusher means is returned toward said starting position by said spring means simultaneously with retraction of said plunger means along said suction stroke, so that in accordance with the selected location of said stop means along said support means a predetermined amount of fluid will be sucked into said barrel by said plunger means, said elongated support means being of a tubular configuration having a hollow interior receiving that part of said plunger means which extends beyond said barrel, said tubular support means having an end distant from said barrel through which said pusher means extends into the hollow interior of said tubular support means into engagement with said plunger means, and said tubular support means being formed with an elongated slot extending longitudinally along said tubular support means, said stop means extending through said slot and carrying a releasable fixing means for releasably fixing said stop means to said tubular support means at a selected location along said slot thereof, and said pusher means having an end region in said tubular support means engaging said plunger means and provided with a projection extending through said slot between said stop means and that end of said slot which is nearest to said barrel so that said stop means will interrupt the movement of said projection of said pusher means during expansion of said spring means for determining the suction stroke of said plunger means, said projection of said pusher means threadedly carrying an adjusting screw which engages said stop means for providing fine adjustment of the suction stroke of said plunger means.

2. A syringe assembly comprising an elongated barrel having one end through which fluid enters into and discharges from said barrel and an opposed open end distant from said one end, plunger means extending through said opposed open end of said barrel into the interior thereof for movement along a pressure stroke in the interior of said barrel toward said one end thereof for discharging fluid from said barrel and for movement in an opposite direction away from said one end thereof along a suction stroke for sucking fluid into said barrel, spring means engaging said barrel and plunger means for urging the latter along said suction stroke thereof, elongated support means extending longitudinally along said plunger means beyond said opposed open end of said barrel and having an end region situated adjacent the latter end of said barrel, connecting means coacting with said elongated support means and said barrel for releasably fixing said elongated support means to said barrel at the region of said opposed open end thereof, pusher means carried by said elongated support means for engaging and pushing said plunger means in opposition to said spring means along said pressure stroke for discharging fluid out of said barrel through said one end thereof, said pusher means when released from pushing said plunger means along said pressure stroke thereof being returned by said spring means toward a starting position simultaneously with retraction of said plunger means along said suction stroke thereof by said spring means, and adjustable stop means carried by said elongated support means at a selected location along the path of movement of said pusher means when released for limiting the extent to which said pusher means is returned toward said starting position by said spring means simultaneously with retraction of said plunger means along said suction stroke, so that in accordance with the selected location of said stop means along said support means a predetermined amount of fluid will be sucked into said barrel by said plunger means, wherein said elongated support means is of a tubular configuration having a hollow interior receiving that part of said plunger means which extends beyond said barrel, said tubular support means having an end distant from said barrel through which said pusher means extends into the hollow interior of said tubular support means into engagement with said plunger means, and said tubular support means being formed with an elongated slot extending longitudinally along said tubular support means, said stop means extending through said slot and carrying a releasable fixing means for releasably fixing said stop means to said tubular support means at a selected location along said slot thereof, and said pusher means having an end region in said tubular support means engaging said plunger means and provided with a projection extending through said slot between said step means and that end of said slot which is nearest to said barrel so that said stop means will interrupt the movement of said projection of said pusher means during expansion of said spring means for determining the suction stroke of said plunger means, and wherein said stop means includes a T-shaped member having one leg situated in the interior of said tubular support means extending transversely across and beyond said slot and a second leg extending through said slot to the exterior of said tubular support means and formed itself with a notch, a strap extending across said notch and said slot of said tubular support means and engaging the exterior surface of the latter, a screw fixed to said T-shaped member and extending longitudinally along said second leg thereof into said notch of the latter, said strap being formed with an opening through which said screw extends, a nut carried by said screw for releasably clamping said stop means to said tubular support means at opposed edge regions of said slot thereof, and wherein said tubular support means has at its exterior a pair of ribs extending along opposite sides of said slot and respectively formed with notches distributed along each rib with the notches of one rib aligned with the notches of the other rib, and all of said notches being located equidistantly from each other, and said strap having a pair of relatively sharp edges located in a pair of successive notches of each rib at a selected position of adjustment of said stop means. 

1. A syringe assembly comprising an elongated barrel having one end through which fluid enters into and discharges from said barrel and an opposed open end distant from said one end, plunger means extending through said opposed open end of said barrel into the interior thereof for movement along a pressure stroke in the interior of said barrel toward said one end thereof for discharging fluid from said barrel and for movement in an opposite direction away from said one end thereof along a suction stroke for sucking fluid into said barrel, spring means engaging said barrel and plunger means for urging the latter along said suction stroke thereof, elongated support means extending longitudinally along said plunger means beyond said opposed open end of said barrel and having an end region situated adjacent the latter end of said barrel, connecting means coacting with said elongated support means and said barrel for releasably fixing said elongated support means to said barrel at the region of said opposed open end thereof, pusher means carried by said elongated support means for engaging and pushing said plunger means in opposition to said spring means along said pressure stroke for discharging fluid out of said barrel through said one end thereof, said pusher means when released from pushing said plunger means along said pressure stroke thereof being returned by said spring means toward a starting position simultaneously with retraction of said plunger means along said suction stroke thereof by said spring means, and adjustable stop means fixedly connectable to said elongated support means at a selected location along the path of movement of said pusher means when released, and mot moving with said pusher means, for limiting the extent to which said pusher means is returned toward said starting position by said spring means simultaneously with retraction of said plunger means along said suction stroke, so that in accordance with the selected location of said stop means along said support means a predetermined amount of fluid will be sucked into said barrel by said plunger means, said elongated support means being of a tubular configuration having a hollow interior receiving that part of said plunger means which extends beyond said barrel, said tubular support means having an end distant from said barrel through which said pusher means extends into the hollow interior of said tubular support means into engagement with said plunger means, and said tubular support means being formed with an elongated slot extending longitudinally along said tubular support means, said stop means extending through said slot and carrying a releasable fixing means for releasably fixing said stop means to said tubular support means at a selected location along said slot thereof, and said pusher means having an end region in said tubular support means engaging said plunger means and provided with a projection extending through said slot between said stop means and that end of said slot which is nearest to said barrel so that said stop means will interrupt the movement of said projection of said pusher means during expansion of said spring means for determining the suction stroke of said plunger means, said projection of saId pusher means threadedly carrying an adjusting screw which engages said stop means for providing fine adjustment of the suction stroke of said plunger means.
 2. A syringe assembly comprising an elongated barrel having one end through which fluid enters into and discharges from said barrel and an opposed open end distant from said one end, plunger means extending through said opposed open end of said barrel into the interior thereof for movement along a pressure stroke in the interior of said barrel toward said one end thereof for discharging fluid from said barrel and for movement in an opposite direction away from said one end thereof along a suction stroke for sucking fluid into said barrel, spring means engaging said barrel and plunger means for urging the latter along said suction stroke thereof, elongated support means extending longitudinally along said plunger means beyond said opposed open end of said barrel and having an end region situated adjacent the latter end of said barrel, connecting means coacting with said elongated support means and said barrel for releasably fixing said elongated support means to said barrel at the region of said opposed open end thereof, pusher means carried by said elongated support means for engaging and pushing said plunger means in opposition to said spring means along said pressure stroke for discharging fluid out of said barrel through said one end thereof, said pusher means when released from pushing said plunger means along said pressure stroke thereof being returned by said spring means toward a starting position simultaneously with retraction of said plunger means along said suction stroke thereof by said spring means, and adjustable stop means carried by said elongated support means at a selected location along the path of movement of said pusher means when released for limiting the extent to which said pusher means is returned toward said starting position by said spring means simultaneously with retraction of said plunger means along said suction stroke, so that in accordance with the selected location of said stop means along said support means a predetermined amount of fluid will be sucked into said barrel by said plunger means, wherein said elongated support means is of a tubular configuration having a hollow interior receiving that part of said plunger means which extends beyond said barrel, said tubular support means having an end distant from said barrel through which said pusher means extends into the hollow interior of said tubular support means into engagement with said plunger means, and said tubular support means being formed with an elongated slot extending longitudinally along said tubular support means, said stop means extending through said slot and carrying a releasable fixing means for releasably fixing said stop means to said tubular support means at a selected location along said slot thereof, and said pusher means having an end region in said tubular support means engaging said plunger means and provided with a projection extending through said slot between said stop means and that end of said slot which is nearest to said barrel so that said stop means will interrupt the movement of said projection of said pusher means during expansion of said spring means for determining the suction stroke of said plunger means, and wherein said stop means includes a T-shaped member having one leg situated in the interior of said tubular support means extending transversely across and beyond said slot and a second leg extending through said slot to the exterior of said tubular support means and formed itself with a notch, a strap extending across said notch and said slot of said tubular support means and engaging the exterior surface of the latter, a screw fixed to said T-shaped member and extending longitudinally along said second leg thereof into said notch of the latter, said strap being formed with an opening through which said screw extends, a nut carried by said screw for releasably clamping said sTop means to said tubular support means at opposed edge regions of said slot thereof, and wherein said tubular support means has at its exterior a pair of ribs extending along opposite sides of said slot and respectively formed with notches distributed along each rib with the notches of one rib aligned with the notches of the other rib, and all of said notches being located equidistantly from each other, and said strap having a pair of relatively sharp edges located in a pair of successive notches of each rib at a selected position of adjustment of said stop means. 